Mechanical movable prop assemblies



y 1968 w. WILKENLOH ETAL 3,383,868

MECHANICALLY MOVABLE PROP ASSEMBLIES 5 Sheets-Sheet 1 Filed Jan. 28, 1966 Fig.7

' lnven l or; w 64:14 u MM 16L y 21, 1968 w. WILKENLQH ETAL 3,383,868

MECHANICALLY MOVABLE PROP ASSEMBLIES Filed Jan. 28, 1966 5 Sheets-Sheet 2 I l /HI l I A? Fig.2

In ven 10m A] ML ill 4 (15.40 A

y 21, 1958 w. WILKENLOH ETAL 3,383,868

MECHANICALLY MOVABLE PROP ASSEMBLIES Filed Jan. 28, 1966 v 5 Sheets-Sheet 3 y 21, 1968 w. WILKENLOH ETAL 3,383,868

MECHANICALLY MOVABLE PROP ASSEMBLIES Filed Jan. 28, 1966 5 Sheets-Sheet 4 "u [9" E M :111: 5]

M Z H (IZ:[ j 25" m lg" n if;

AM 9n E111? Q: 11:11 WW '9" :3 2 ll 1 :51]

M V/gu MN [I -j r ih 2: '25" m" Fig.4

May 21, 1968 Filed Jan.

W. WILKENLOH ETAL MECHANICALLY MOVABLE PROP ASSEMBLIES 5 Sheets-Sheet 5 3,383,868 Patented May 1968 17 Claims. Cl. 61-45) ABSTRACT OF THE DISCLOSURE A prop arrangement for use in mine galleries including at least two prop assemblies arranged spaced from each other and movable independent from each other toward and away from a face of the mine gallery and each including at least one extensible and retractable prop member supported at its lower end on a base member shiftable on the floor of the mine gallery and carrying a cap member on its upper end adapted to engage the roof of the mine gallery, shield means extending transverse to the direction of movement of the prop assemblies and adapted to engage the roof in the region between the cap members and the mine face, and extensible and retractable connecting means connecting at least two adjacent prop assemblies with a common shield means for moving the common shield means and the prop assemblies connected thereto relative to each other in direction of movement of the prop assemblies.

The present invention relates to mechanically movable prop arrangements for use in a mine gallery or the like for supporting the roof of the mine gallery. Prop arrangements are known in the art which include a plurality of units or prop assemblies in the form of frames including elongated cap members, base members and a plurality of extensible and retractable prop members extending between the base members and the cap members, which are arranged movable as units spaced from each other, whereby the units carry on their cap members extensible and retractable shield means to support the roof of the mine gallery forwardly of the front ends of the cap members.

It is known to move the shield means of mechanically movable units by means of hydraulically operated cylinder and piston means carried by the cap members of the respective unit to a position in which the shield means support the roof adjacent to the face of the gallery. It is also known to mount the means which connect the shield means to the respective cap members pivotally on the latter and to provide additional means cooperating with the pivotally mounted connecting means in such a manner as to press the shield means against the roof of the mine gallery.

Double acting hydraulically operated moving cylinders are usually employed for moving the prop assemblies in a direction toward the face of the mine gallery. These moving cylinders are carried by the prop assemblies and the piston rods thereof are pivotally connected in the region of the free ends thereof to transporting means located between the face of the mine gallery and the plurality of prop assemblies. By feeding pressure fluid to the side of the piston of the moving cylinder facing away from the face of the mine gallery, the piston rods will be extended so that the transporting means are moved in direction transverse to their elongation toward the face of the mine shaft, whereby the moving cylinders are braced by the respective prop assemblies, the prop members of which are expanded so as to press the cap and base member thereof respectively against the roof and the floor of the mine gallery. After thus moving the transporting means in transverse direction, the movable .prop assemblies are moved in the same direction by feeding pressure fluid to the other side of the piston in the moving cylinder. During this movement the transporting means serve as abutment to which the moving cylinders are connected by means of the piston rods.

'It is also known to connect two adjacent prop assemblies by means of a moving cylinder and guide means in such a manner with each other that the thus connected adjacent prop assemblies may be moved in successive steps relative to each other, whereby during movement of one of the thus connected prop assemblies the other prop assembly serves as abutment for the moving prop assembly. The moving cylinder is in such an arrangement mounted on one of the adjacent prop asemblies and the piston rod of the moving cylinder is connected to the other prop assembly.

The prop members of the moving prop assembly are retracted so that the cap members thereof and the shield means connected thereto are slightly downwardly spaced rom the roof of the mine gallery and after the respective prop assembly has been moved through the desired distance, the prop members thereof will be extended again so that the cap carried thereby and the shield means will abut against the roof of the mine gallery to properly support the roof again. In this operation the roof is therefore not supported during movement of the prop arrangement. The danger therefore exists that the unsupported roof portion will collapse or that at least portions thereof will tumble on the transporting means and endanger the workmen working in the vicinity thereof.

It is an object of the present invention to provide for a prop arrangement including a plurality of movable prop assemblies constructed and arranged in such a manner that the roof of the mine gallery is properly supported during movement of the prop assemblies toward the face of the mine gallery.

With these objects in view, the prop arrangement according to the present invention which is adapted to be used in mine galleries and the like mainly includes a plurality of elongated prop asemblies arranged spaced and substantially parallel to each other and movable in direction of their elongation independent from each other, and each including at least one elongated cap member having a front end adapted to be directed to a face of the mine gallery and a top face adapted to engage the roof of the mine gallery; a pair of extensible and retractable prop members for each cap member and connected at the upper ends thereof to the cap member, and a base member connected to the lower end of each prop member. The arrangement includes further a plurality of shield means extending transverse to the cap members and forwardly of the front end thereof, connecting means connecting the plurality of shield means respectively to cap members of adjacent prop assemblies which are movable independent of each other, and means carried by the cap members and cooperating with the connecting means for extending and retracting the same for moving the shield means and the respective cap member relative to each other. In this arrangement the shield means may therefore be held in contact with the roof of the mine gallery by at least one of the prop assemblies which is connected thereto while the other prop assembly connected thereto is moved toward the face of the gallery.

The means for moving the shield means relative to the prop assemblies to which they are connected preferably include hydraulically operated cylinder and piston means and the cylinder means thereof are preferably pivotally mounted on the respective cap members for tilting movement about a tilting axis extending transverse to the elonu gation of the cap members. The arrangement includes preferably further means for tilting the respective cylinder means about the tilting axis thereof.

The arrangement preferably also includes moving cylinders operatively connected to the prop assemblies for moving the same in direction of their elongation toward the face of the mine gallery. The piston rod of the piston in the moving cylinder may be connected to elongated transport means located between the face of the mine gallery and the plurality of prop assemblies, or adjacent prop assemblies may be connected by a. moving cylinder and appropriate guide means in such a manner that the moving cylinder will be braced during movement of one of the adjacent prop assemblies on the other prop assembly so that the pair of prop assemblies may be moved one after the other towards the mine face. In the last mentioned arrangement a common shield means is connected to at least two adjacent prop assemblies movable relative thereto in direction of the elongation of the respective prop assemblies.

This arrangement has the additional advantage that each prop assembly during the movement thereof is not only connected and braced through the moving cylinder to the adjacent prop assembly, but is also connected thereto by the common shield means which during movement of the moving prop assembly is held in tight engagement with the roof of the mine shaft. Thereby, the cylinder and piston means which serve to move the shield means and the respective cap member relative to each other serve also as an additional guide for the moving prop assembly.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional Objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic side view of a prop arrangement according to the present invention; and

FIGS. 2-5 are respectively schematic top views of prop arrangements according to the present invention.

Referring now to the drawings, and more specifically to FIG. 1, it will be seen that a prop assembly may include four extensible prop members 1 arranged at the corners of a rectangle, only the front ones are shown in FIG. 1, and which are connected in pairs at the upper ends thereof by a cap member 2 and which carry on bottom ends thereof base members 3. A hollow member or U-shaped beam 4 is arranged between the prop members 1 adjacent to the bottom ends thereof and connected thereto. The beam 4 carries in the interior thereof a moving cylinder 5. Each of the prop members 1 comprises a lower part In forming a prop cylinder which is connected at the lower end thereof by means of a ball and socket joint 6 to the respective base member 3. The up per part 1b of each prop member 1 is in the form of a piston slidably guided in the lower cylinder part 1a and the piston part 1b is preferably pivotally connected at its upper end to the respective cap member 2, the side walls 2a extend spaced from each other downwardly from a top wall of the respective cap member.

Prop assemblies of the aforementioned kind are known in the art. In order to move the assembly toward the face of a mine gallery, not shown in FIG. 1, the piston rod 5a of the piston (not shown in the drawings) slidably guided in the cylinder 5 is connected by means of a bolt 8 to a fork member 7b carried by a bracket 7a of elongated transport means 7 extending longitudinally along the face of the mine gallery.

When the piston rod 5a is moved out of the moving cylinder 5 by feeding pressure fluid to one side of the piston, the elongated transporting means 7 will be moved in direction of the arrow P toward the non illustrated face of the mine gallery. During this movement the prop members 1 are extended so that the base members 3 are pressed against the floor and the cap members 2 against the roof of the mine gallery so that the prop assembly serves as an abutment for the cylinder 5. Subsequently thereto, the prop assembly as moved also in direction of the arrow P by feeding pressure fluid to the other side of the piston in the moving cylinder 5 so that the piston rod is retracted and so that the prop assembly assumes again a. position relative to the elongated transport means 7 as shown in FIG. 1. During this movement of the prop assembly the prop members 1 are slightly collapsed at least to such an extent that the upper surfaces of the cap members 2 are not pressed against the roof of the mine gallery and during this movement of the prop assembly the elongated transport means 7 forms the stationary abutrent.

As shown in FIG. 1 shield means 11 are arranged transverse to and forwardly of the front ends of the cap members 2 and the shield means 11 are connected to each cap member by a cylinder 9 pivotally mounted for tilting movement about a tilting axis 10 at the front end of the respective cap member and a piston rod 9a of a piston, not shown in FIG. 1, which is slidably guided in the cylinder 9. Means are provided for tilting the cylin der 9 about the tilting axis 10 and these means preferably include a cylinder member 12 fixedly mounted on the rear end of the cylinder and a piston member 12a slidably guided in the cylinder member 12. The end of the piston member 12a which extends beyond the cylinder member 12 abuts against an abutment member 13 mounted on the cap 2. By moving the piston rod 9a relative to the piston 9 in direction of the arrow D in one or the other direction, the shield means 11 connected thereto may be moved toward or away from the front end of the cap 2 and by moving the piston member 12a relative to the cylinder member 12 in one or the other direction as indicated by the arrow C, for instance from the position 11 to the position 11a as indicated in full lines in FIG. 1 and in each of these shifted positions the cylinder member 9 may be tilted about its tilting axis 10 and thereby the shield means may be raised or lowered respectively to the positions 11', 11 and 110, 11a as indicated in dotted lines.

The arrangement illustrated in FIG. 1 and above described has been mentioned only as an example to explain one way of moving such a prop arrangement. Evidently, the pivotally arranged cylinder and piston means 9, 9a carrying the shield means 11 and the cylinder and piston member 12 and 12a connected to the cylinder means 9 for tilting the same about its tilting axis 10 may also be used in prop assemblies differing from the above-described arrangement.

FIG. 2 illustrates schematically a prop arrangement according to the present invention for supporting the roof of a mine gallery having a face 20, for instance a seam of coal which is mined, for instance, by a mining apparatus of known construction, not shown in the drawing. The mining apparatus is thereby advanced in the direction of the arrow E to mine the seam for a width equal to the end face 21. Usually, elongated transporting means extending parallel to the face 20 are provided adjacent to the latter, but these transporting means are not shown in FIG. 2. A plurality of adjacent prop assemblies described in connection with FIG. 1 and respectively numbered I-VI are arranged spaced and substantially parallel to each other extending substantially normal to the face 20 of the mine gallery. For reason of simplification the moving cylinders 5 connected to each prop assembly are not shown in FIG. 2 which only schematically illustrate the cap members 2' of the elongated prop assemblies.

As shown in FIG. 2 a common shield means 11 is provided for each pair of adjacent prop assemblies. The common shield means 11 for each adjacent pair of prop assemblies are connected movably toward and away from the front ends of the respective caps 2 by cylinder and piston means 9, whereby the cylinder and piston means 9 are carried only by the inner cap members 2' of adjacent pairs of prop assemblies. The cylinder and piston means 9 are again pivotally mounted for tilting move ment about a tilting axis 10 extending transverse to the respective cap member as described in connection with FIG. 1 and a cylinder member 12 as shown in FIG. 1 with its piston member 12a abutting against an abutment member 13 on the respective cap member is also provided in the arrangement as shown in FIG. 2 for each cylinder and piston means 9 for tilting the latter about its pivot axis. The cylinder member 12 connected to the cylinder and piston means 9 and the piston member 12a cooperating with the piston 12 are however not shown in FIG. 2. Each shield means 11 is of rectangular form and has a length substantially equal or slightly longer to the distance between the outermost cap members of each pair of adjacent prop assemblies. Each shield means 11 is carried therefore by two cylinder and piston means 9 and pressed against the roof of the mine gallery.

As shown in FIG. 2, the piston rods of the cylinder and piston means 9 of the prop assemblies I and II are fully retracted. The shield mean 11 of these two prop assemblies is therefore arranged closely to the front ends of the caps 2' of the aforementioned prop assemblies and supports in this way the roof of the mine gallery between the face 2 0 and the front ends of the cap 2. When the face of the seam is mined to a certain depth, as indicated in FIG. 2, the piston rods of the cylinder and piston means 9 are extended as shown for the prop assemblies III and IV so that the shield means 11 connected to these prop assemblies is again located at the advanced face of the seam to support the roof closely adjacent to this face.

To advance the shield means in the aforementioned manner it is only necessary to slightly reduce. the pressure thereof against the roof by releasing some pressure fiuid from the tilting cylinders 12 so that the shield means 11 may be advanced by means of the cylinder and piston means 9. During this advancement of the shield means 11 it is therefore not necessary to move the latter downwardly for a considerable distance away from the mine roof so that the latter will be still supported to a certain extent during advancement of the shield means 11.

In order to subsequently advance the prop assemblies to a position in which the front end of the caps 2' thereof are again closely adjacent to the shield means 11 supported by the same, pressure fluid is fed into the moving cylinder (not shown in FIG. 2) of the respective prop assembly in the manner as described in connection with FIG. 1 to advance the respective prop assembly while at the same time the piston rod of the cylinder and piston means 9 is retracted. The advance of the prop assembly may be supported by feeding pressure fluid into the cylinders 9 to the other sides of the pistons so that, as the piston rods 9a are retracted into the respective cylinder means 9 while the shield means 11 connected to the piston rods 9a is tightly pressed against the mine roof, a pull is exerted on the prop assemblies connected thereto. Under certain conditions the advancement of the prop assemblies may be produced solely under the action of the cylinder and piston means 9 so that provision of a special moving cylinder will not be necessary. In this case the two frames of each prop assembly I-VI, shown in FIG. 2, are simply connected to each other for simultaneous movement.

FIG. 3 shows another arrangement according to the present invention in which adjacent prop assemblies I and II, III and IV, V and VI are connected to each other by a moving cylinder 25. The moving cylinder 25 is connected by connecting means 26 of known construction to a member, similar to the element 4 shown in FIG. 1 which is connected to the lower ends of the prop members 1 of the respective prop assembly, and as shown in FIG. 3 the moving cylinders 25 are connected by the connecting means 26 respectively to the prop assemblies I, III and V. The piston rods 27, only schematically indicated in FIG. 3, of the various moving cylinders 5 extend to opposite sides thereof and are respectively connected by connecting means 28 to the other prop assembly forming each pair of prop assemblies shown in FIG. 3, that is to the prop assemblies II, IV and VI. In this way it is possible by feeding pressure fluid to one or the other side of the piston in the moving cylinder 25 to advance the prop assemblies connected thereto in steps, whereby during advancement of one prop assembly, the other prop assembly of each pair provides a proper abutment.

In the arrangement shown in FIG. 3 each of the prop assemblies is provided with cylinder and piston means 9 tiltably carried in the manner as described before on the cap member of the respective prop assembly and the piston rods of the cylinder and piston means 9 of each pair .of adjacent prop assemblies carry a common shield means 11 which is pressed against the mine roof in the manner as described before. The piston rods of the cylinder and piston means 9 for the prop assemblies I and II of FIG. 3 are withdrawn so that the front ends of the cap members of the aforementioned prop assemblies are closely adjacent to the shield means 11 carried thereby, while the piston rods for the prop assemblies III and 'IV are fully extended. The prop assembly VI is shown in FIG. 3 already advanced so that the front end thereof is closely adjacent to the shield means 11' connected thereto and of course the prop assemblies -III, IV and V will be subsequently likewise advanced so that the front ends thereof will be located adjacent to the shield means 11 connected thereto.

The arrangement shown in FIG. 4 is very similar to the above-discussed arrangement illustrated in FIG. 3. The difference between the two arrangements is that in the arrangement in FIG. 4 two adjacent pairs of prop assemblies carry a common shield means 11". The prop assemblies of each pair of prop assemblies are again connected to each other by means of a moving cylinder 25" to be moved relative to each other in the manner as described above and each of the prop assemblies has tiltably mounted cylinder and piston means 9" and the piston rods of two adjacent pairs of prop assemblies carry a common shield means 11", the length of which is therefore slightly larger than the distance between the outermost prop assemblies of two adjacent pairs of prop assemblies. The piston rods of the cylinder and piston means '9" of the prop assemblies 1' to IV are shown completely retracted, while the shield means 11 carried by the prop assemblies V to VIII is advanced to a new position to be closely adjacent the advanced mine face and the prop assembly VIII is shown in FIG. 4 in an already advanced position closely adjacent to the shield means 1 1 connected thereto.

The arrangement shown in FIG. 5 is similar to the arrangement above described in connection with MG. 2. In the arrangement shown in FIG. 5 the length of each shield means 11" coordinated with two adjacent prop assemblies is however slightly shorter than the distance between facing edge portions of the outermost cap members 2" of two adjacent prop assemblies. The shield means 11 are carried in the same manner as described in connection with FIG. 2 on the piston rods of cylinder and piston means 9" tiltably mounted on the inner cap members 2" of adjacent pairs of prop assemblies. The tiltable cylinder and piston means 9 in the arrangement shown in FIG. 5 are of course again tilted about their tilting axis by cylinders and pistons connected thereto as described in connection with FIG. 1 so that the respective shield means 11 may be pressed against the mine roof or be placed out of engagement with the latter. The outermost cap members 2" .of each of two adjacent prop assemblies are longer than the innercap members of adjacent pairs of prop assemblies by a distance substan- 7 tially equal to the width of the shield means 11" so that when the piston rods of the cylinder and piston means 9 are completely retracted the front edges of the outermost cap members 2 adjacent pairs of prop assemblies are in line with the front edge of the respective shield means 11".

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of prop arrangements for use in mine galleries, differing from the types described above.

While the invention has been illustrated and described as embodied in a prop arrangement for use in a mine gallery including a plurality of elongated prop assemblies and shield means carried thereby movable between a retracted and advanced position relative to the prop assemblies, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A prop arrangement adapted to be used in mine galleries and the like comprising, in combination, a plurality of elongated prop assemblies arranged spaced and substantially parallel to each other movable in direction of their elongation independent from each other and each including at least one elongated cap member having a front end adapted to be directed to the face of a mine gallery and a top face adapted to engage the roof of the mine gallery, a pair of extensible and retractable prop members for each cap member and connected at the upper ends thereof to said cap member and a base member connected to the lower end of each prop member; a plurality of shield means extending transverse to said cap members and forwardly of the front ends thereof; extensible and retractable connecting means connecting each of the plurality of shield means respectively to capmembers of at least one pair of adjacent prop assemblies which are movable independent of each other for moving the shield means and each of said independently movable prop assemblies, the cap members of which are connected to a common shield means, relative to each other and to said common shield means in direction of the elongation of said cap members.

2. A prop arrangement as set forth in claim 1 wherein each of said connecting means includes fluid operated cylinder and piston means.

3. A prop arrangement as set forth in claim 1, wherein each of said connecting means includes an elongated member mounted on the respective cap member tiltable about a tilting axis extending transverse to the elongation of the cap member, and means carried by the respective cap member and connected to the respective elongated member for tilting the latter about said tilting axis.

4. A prop arrangement as set forth in claim 1, wherein each of said connecting means includes a hydraulic cylinder and piston means, said cylinder means being mounted on the respective cap member tiltable about a pivot axis extending transverse to the elongation of the cap member, and means carried by the respective cap member and connected to the cylinder means carried thereby for tilting the latter about said tilting axis.

5. A prop arrangement as set forth in claim 1, wherein each of said connecting means includes hydraulically operated cylinder and piston means, said cylinder means being mounted on the respective cap member tiltable about a tilting axis extending transverse to the cap member, and a piston rod fixed at one end to the respective piston means and connected at the other end thereof to the respective shield means, and including tilting means connected to said piston means for tilting the latter about said pivot axis.

6. A prop arrangement as set forth in claim '5, wherein each of said tilting means includes a cylinder member and a piston member slidably guided in said cylinder member, one of said members being connected to the respective cylinder means at a portion of the latter spaced from said tilting axis and the other of said members engaging the respective cap member.

7. A prop arrangement as set forth in claim 6, and including a plurality of moving means operatively connected to said prop assemblies for moving each of said prop assemblies during actuation of the respective moving means independent from the other prop assembly a given distance in direction of the elongation thereof, each of said shield means having a substantially rectangular shape having a width substantially equal to said given distance.

8. A prop arrangement as set forth in claim 6, and including a moving cylinder means for each pair of adjacent prop assemblies and operatively connected to said pair of adjacent prop assemblies for selectively moving each prop assembly of the pair in direction of its elongation through a given distance in such a manner that the moving cylinder means moving one of said pair of prop assemblies is braced by the other prop assembly of the pair of prop assemblies, each of said shield means having a substantially rectangular shape and a width subtantially equal to said given distance.

9. A prop assembly as set forth in claim 8, wherein a common shield means is provided for each pair of adjacent prop assemblies.

10. A prop assembly as set forth in claim 8, wherein a common shield means is provided for each two pairs of adjacent prop assemblies.

11. A prop assembly as set forth in claim 10, wherein at least one of each pair of two adjacent pairs of prop assemblies includes cylinder and piston means having piston rods connected to the common shield means of the two pairs of adjacent prop assemblies.

12. A prop arrangement as set forth in claim 11, wherein each of said two pairs of adjacent prop assemblies includes cylinder and piston means, the piston rods thereof being connected to said common shield means of the two pairs of adjacent prop assemblies, and wherein each of said common shield means has a length slightly longer than the distance between the two outermost prop assemblies of said two adjacent pairs of prop assemblies.

13. A prop arrangement as set forth in claim '7, wherein each prop assembly includes two cap members and wherein only the cap member of each two adjacent prop assemblies which is adjacent the cap member of the adjacent prop assembly includes cylinder and piston means, the piston rods thereof being connected to said comm-on shield means of the two adjacent prop assemblies.

14. A prop arrangement as set forth in claim 13, wherein said common shield means has a length slightly longer than the distance between the outermost cap member of the two adjacent prop assemblies.

15. A prop arrangement as set forth in claim 13, wherein said common shield means has a length slightly longer than half the distance between the outermost cap members of the two adjacent prop assemblies.

16. A prop arrangement as set forth in claim 15, wherein the outermost cap member of each two adjacent prop assemblies is longer by a dimension substantially equal to the width of the common shield means than the other cap member of each prop assembly.

17. A prop arrangement adapted to be used in mine galleries and the like, comprising in combination, at least two prop assemblies arr-anged spaced from each other and movable in the direction toward the mine face of the mine gallery independent from each other and each including at least one extensible and retractable prop member, said p-r-op member being supported with its lower end on a base member shiftable on the floor of the mine gallery and being provided with a cap member arranged on the upper end of the prop member and adapted to engage the roof of the mine gallery; shield means extending transverse to the direction of movement of the prop assemblies forward-1y from the latter and adapted to engage :the roof in the region between said cap members and the mining face; and connecting means connecting at least two adjacent prop assemblies with a common shield means for moving the shield means and each of the prop assemblies connected to said common shield means relative to each other and to said common shield means in the direction of movement of said prop assemblies.

References Cited FOREIGN PATENTS JACOB SHAPIRO, Primary Examiner. 

